Lucent Vesicles Research Articles

The Ultrastructure of the Nervous System ofGyratrix hermaphroditus(Turbellaria, Rhabdocoela)

The fine structure of the nerve cells in the brain of Gyratrix hermaphroditus is studied as well as the structure of the neuropile. General features of all nerve cells are a prominent neucleus with a small nucleolus, a scanty layer of cytoplasm containing mitochondria, free ribosomes, few profiles of granular endoplasmic reticulum, smooth endoplasmic reticulum, subsurface cisternae, well developed Golgi complexes, multivesicular bodies and numerous vesicles diagnostic for different nerve cell types. On the basis of the vesicle content four nerve cell types can be distinguished. The following types of vesicles are observed. Dense cored vesicles (50–80 nm), dense vesicles (60–120 nm), small lucent (synaptic) vesicles (40–50 nm), large lucent vesicles (50–200 nm) and lysosome-like vesicles (200–500 nm). The significance of the variations in the interior electron dense material of the multivesicular bodies is discussed.

The Ultrastructure of the Nervous System ofGyratrix hermaphroditus(Turbellaria, Rhabdocoela)

The peripheral nervous system and the synapses of G. hermaphroditus are studied with the electron microscope. There is a submuscular as well as a subepithelial plexus. The subepithelial plexus is found among the muscles and between the muscles and the basement membrane. It consists of fibres containing large lucent and lysosome-like vesicles and fibres with only small lucent (synaptic) vesicles. In the deeper lying submuscular plexus also dense and dense-cored vesicles occur in the fibres. Cell bodies are not observed in the plexuses. The separate nerve supplies of the pharynx and the gonads contain nerve cells of the neurosecretory type. Fibres of the same kinds as in the brain are also seen here. The synapses in the neuropile are of two kinds. 1. Symmetrical synapses with an additional presynaptic network are most common. 2. Synapses without thickenings of membranes are observed between lateral membranes of neurites. In the peripheral nervous system are two other kinds of synapses also observed. 1. Asymmertical synapses with a denser and wider postsynaptic thickening and 2. neuromuscular junctions. Neurites containing accumulations of small vesicles against the basement membrane are also described. The organization of the peripheral nervous system is described and discussed in relation to the systematic position of G. hermaphroditus.

Ultrastructure of the corpus cardiacum and corpus allatum of the house cricket Acheta domesticus.

The ultrastructure of the corpus cardiacum (CC) and corpus allatum (CA) of the house cricket, Acheta domesticus, is described. Axon profiles within the CC contain neurosecretory granules 160-350 nm in diameter which are indistinguishable from those found in type I neurosecretory cells of the pars intercerebralis and in the nervus corporis cardiaci I. The CC itself contains two cell types: intrinsic neurosecretory cells and glial cells. Intrinsic NSC cytoplasm contains Golgi bodies and electron dense neurosecretory granules 160-350 nm in diameter. Synaptoid configurations with 20-50 nm diameter electron lucent vesicles were observed within axon profiles of the CC. The structure of the CA is relatively uniform with one cell type predominating. Typical CA cells possess large nucleoli, active Golgi complexes, numerous mitochondria, and occassional microtubules. Groups of dark staining cells scattered throughout the CA of some animals were interpreted as evidence of cellular death.

Innervation of the periarteriolar lymphatic sheath of the spleen

During the course of a neurohistochemical and two independent electron microscopic studies of the mouse spleen, unmyelinated adrenergic nerves containing numerous dense core and lucent vesicles and devoid of neurolemma were observed adjacent to reticular cells and lymphocytes in the white pulp. Some of these nerves formed an intimate relationship with these cells. Since adrenergic substances have been reported to modulate the cell cycle of lymphocytes in vitro, these findings are suggestive of a neural influence on the cell cycle of lymphocytes in vivo.

Mapping and ultrastructure of neurosecretory cells in the brain of Helix aspersa

1. 1. The brain of Helix aspersa contain three types of neurosecretory cells (DGC, LGC and YC), classified on the basis of the reaction of the neurosecretory products with Alcian Blue/Alcian Yellow technique. 2. 2. The monopolar DGC. and mono-, and bipolar LGC are Chrome-Haematoxylin positive, but the monopolar YC are CH-negative. 3. 3. The cells and their terminals contained granules of 1500–1800Å in diameter and electron lucent vesicles of similar diameter range. 4. 4. It is suggested that the neurosecretory products are released by diffusion, exocytosis or/and intracellular breakdown.

Zinc iodide-osmium tetroxide reaction: its effect on the synaptic vesicles in locust neuromuscular junctions and its chemical basis

The zinc iodide-osmium tetroxide reaction (ZIO) was first used in neurobiological research by Maillet (Bull. Ass. Anat. 53, 233; 1968). Subsequently several authors have shown that, under appropriate conditions, ZIO stains mainly the interior of synaptic vesicles. The substrate of this reaction is under discussion, since ZIO can also react with other subcellular structures in a variety of tissues, e. g. mitochondria, endoplasmic reticulum, dictyosomes and lysosomes. Additionally, in vitro substances as different as some aminoacids, catecholamines, aldehydes and phospholipids (Pellegrino de Iraldi, Experientia 33, 1; 1977) can yield black precipitations with ZIO.Our studies were done with the motor nerve terminals at the femoral retractor unguis muscle of the locust (Locusta migratoria). These terminals are chiefly the endings of excitatory motoraxons and are characterized by the presence of electron lucent vesicles and by an accumulation of mitochondria.

Ultrastructural and morphometric study of the lung of the European salamander, Salamandra salamandra L.

Ultrastructural and morphometric investigations were performed on the lung of the European salamander, Salamandra salamandra L. Folds of first and second order are covered with a ciliated epithelium containing goblet cells. The respiratory surface of the lung is lined by a single type of cell which, in amphibians, combines features of type I and type II alveolar cells of the mammalian lung. In the salamander the respiratory and ciliated epithelial cells as well as goblet cells possess electron dense and lucent vesicles in their cytoplasm as well as lamellar bodies. A small amount of surfactant, composed most probably of phospholipids and mucopolysaccharides, was observed covering the entire inner surface of the lung. Morphometric methods were used to determine the dimensions of the perinuclear region of pneumocytes, the thickness of the air-blood barrier and lung wall, and also the diameter of capillaries. The thickness of the respiratory air-blood barrier was found to be considerably higher than that of the corresponding barrier in mammals.

DISTRIBUTION OF MATURATION-PROMOTING FACTOR IN STARFISH OOCYTE STRATIFIED BY CENTRIFUGATION.

In starfish, cytoplasm taken from maturing oocytes is capable of inducing breakdown of the germinal vesicle and subsequent maturation when injected into immature oocytes. The cytoplasmic factor has been designated as "maturation-promoting factor" (MPF). Ooplasm was stratified by centrifugation of maturing oocytes in density-graded Ficoll-seawater, without disrupting the cell. Three strata were distinguished beginning with the centripetal side: oil cap, hyaline layer and yellow layer. MPF activity was shown to be localized in the hyaline layer. Electron microscopic observation revealed that the hyaline layer contains Golgi complexes, many lucent vesicles and multi-vesicular bodies as distinct organelles, but seldom contains such inclusions as the lipid droplets forming the oil cap, mitochondria, yolk and pigment granules contained in the yellow layer. Based on these observations, a possible cytoplasmic component with MPF activity is discussed.

The connections of the sensory organ of Bellonci with the brain in Isopoda (crustacea).

The peduncle linking the organ of Bellonci with the brain was examined in Sphaeroma serratum and Anilocra frontalis. This peduncle, in its extension to the brain, becomes a nerve-like tract with bundles of pedicles originating from the sensory cell bodies located in the organ of Bellonci. It ends at the level of the medulla interna in an alveolar region resulting from the swelling of the sensory pedicle terminations. At this level three types of connections have been observed. The first is characterized by afferent synapses to the brain with, in the sensory pedicle endings, structures similar to the presynaptic ribbons noted by some authors in photoreceptors of arthropods. The two other types include nerve fibres originating from the brain, one with small electron lucent vesicles, a second displaying larger vesicles with a core of medium density. These fibres form efferent synapses to the organ of Bellonci. The sensory differentiation of the organ of Bellonci in Isopoda is confirmed but its true role is not specified.

Acetylcholinesterase and synapses in the nervous system of Phocanema decipiens (Nematoda): a histochemical and ultrastructural study

The nervous system of Phocanema decipiens was examined histochemically for acetylcholinesterases (EC 3.1.1.7) using the acetylthiocholine method with specific inhibitors (eserine and diisopropylfluorophosphate) and different substrates (butyrylthiocholine and acetylthiocholine). The enzymes, which are localized mainly as small discrete granules, are found in the nerve ring, the six longitudinal nerve cords, and the three pharyngeal nerves. With the electron microscope, these neurons are found to contain presumptive cholinergic synaptic contacts with aggregations of small lucent vesicles in the presynaptic axons. In the nerve ring, such synapses are observed in axoaxonal, neuromuscular and axoglial cell contacts. The longitudinal nerve cords have neuromuscular junctions similar to those observed in other nematodes. In the four sublateral nerve cords, the alternating regions with and without synaptic contacts correspond to the discontinuous histochemical pattern of enzymatic activity. The pharyngeal nerves have axoaxonal and axooesophageal musculature synapses. In most of the synapses, some large dense or dense-core vesicles are found intermingled with the small lucent vesicles. This coexistence of different vesicles is discussed in the light of the cholinergic link hypothesis, whereby acetylcholine is initially released to facilitate the release of other neurotransmitters.

Synaptoid profiles in regenerating crustacean peripheral nerves.

Synapse-like structures occurring in regenerating crayfish peripheral nerves are characterized by aggregates of small (250 to 600 A) electron lucent vesicles adjacent to a thickened "presynaptic" membrane. Such synaptoid profiles are seen opposite other axons, glial processes or extracellular fibrous material. Junctions with cellular elements do not show "postsynaptic" specializations. These complexes are compared to axo-glial synapses in the developing spinal cord and to synaptoid configurations observed by others in vertebrate and invertebrate neurosecretory systems.

Localized catecholamine storage associated with granules in murine neuroblastoma cells

Catecholamine storage was examined in cultures of the marine neuroblastoma cell line, N-TD6, using histofluorescence, electron microscopic, isotopic and radioautographic criteria. This line was originally derived from uncloned, C1300 tumor cells by selection in tyrosine deficient medium. N-TD6 cells possess both tyrosine hydroxylase (tyrosine-3-monooxygenase, EC 1.14.16.2) and dopamine β-hydroxylase (dopamine β-monooxygenase, EC 1.14.17.1) activities. When examined for paraformaldehyde-induced histofluorescence, a small percentage of cells in the population show intense catecholamine fluorescence, often localized within discrete regions of the cellular processes. Electron microscopic examination of these cells reveals both electron lucent vesicles and more frequent, electron dense granules, 50–70 nm and 100–300 nm in diameter, respectively. The distribution of these granules and vesicles varies, but they appear most numerous near the cell surface, along processes within process endings. By labeling cells with [ 3H]dopamine and then allowing the cells to release unbound label in the presence of unlabeled dopamine, the localization of catecholamine stores was visualized by radioautographic techniques. While a variety of intracellular distributions of radioactivity were observed, the most prominent concentrations were found in the processes and their terminals; no labeled material was retained when reserpine was present during uptake. The topographic coincidence of granules, catecholamine fluorescence and [ 3H]dopamine retention in these neuroblastoma cells suggests that catecholamines are stored within these granules in a manner analogous to that observed in normal adrenergic neurons.

Electron microscopic studies of the development of new neurohaemal contacts in the median eminence of the rat after hypophysectomy

In the normal rat the axons of the parvicellular neurosecretory system form terminals which are characterised by dense core vesicles of 80–160 nm diameter and which lie against the fenestrated portal capillaries in the upper neurohypophysis (median eminence). The magnocellular neurosecretory axons traverse the interanal zone of the median eminence and form terminals against the fenestrated capillaries of the distal neurohypophysis (neural lobe). In the neural lobe it is assumed that the more electron dense vesicles (of around 200 nm diameter) characterise the vasopressin containing terminals of neurones in the supraoptic nucleus and that the less numerous terminals with the more electron lucent vesicles (also of around 200 nm diameter) belong to the axons of the paraventricular neurones and contain oxytocin. For the first few days after hypophysectomy, the proximal stumps of the cut neurosecretory axons in the internal zone of the median eminence are distended with neurosecretory material while axonal sprouts which are rich in neurotubules and completely ensheathed in satellite cell cytoplasm gradually penetrate the external zone. Subsequently there is a massive hypertrophy of fenestrated capillaries and the newly formed axonal sprouts progressively lose their satellite cell cover and thus acquire neurohaemal contacts with the outer basement membrane of the perivascular space. The development of these contacts is associated with the appearance of increasing numbers of synaptic vesicles and prejunctional dense projections. This reconstitution of the morphological features of the normal neurohaemal contacts is associated with recovery of antidiuretic function. In the hypertrophic median eminence the neurosecretory axon terminals with the electron lucent type of vesicles far outnumber those with the electron dense vesicles. It is suggested that the greater degree of cell loss from the supraoptic as opposed to the paraventricular nuclei puts the paraventricular axons at an advantage in competing for space on the basement membrane around the perivascular space of the newly formed capillaries. It is suggested that an important factor in promoting the regeneration of the neurosecretory axons is the remarkable hypertrophy of the fenestrated capillaries against which they come to terminate.

Ultrastructure of sinus venosus innervation in Petromyzon marinus

Sections of the sinus venosus from the young adult Petromyzon marinus revealed the presence of numerous axon profiles. These nonmyelinated axons are bound singly or in multiples within Schwann cell sheaths. At points of neuromuscular association, the axon protrudes from an incomplete Schwann cell investment and approaches within 40–50 nm of adjacent myocardial sarcolemmae with only basal laminae intervening between the two. Points of neuromuscular association are characterized by the presence of abundant electron lucent vesicles (40–50 nm in diameter) within the axon crowded against the axon membrane nearest the myocardial cell. No axons were observed within the atria or ventricles. Innervation of chromaffin cells containing 120 nm vesicles with electron dense cores was not observed.

Electron microscopic studies on the pars intermedia in normal and in mice with hereditary nephrogenic diabetes insipidus.

The ultrastructure of the pars intermedia (PI) of the normal VII +/+ and hereditary nephrogenic diabetes inspidus DI Os/+ mice has been studied with particular reference to the morphology of the glandular cells and their innervation. Four types of cells were observed in both the genotypes of mice, 1) the light glandular cell, 2) the dark cell, 3) a type of cell similar to ependymal cells and 4) a small percentage of typical ACTH cells, observed mostly on the PI border of the cleft and rarely in the centre of PI. The predominant light glandular cells contain mainly two types of membrane bound granules: 1) electron dense core granules, which measure 1500–2500 A and 2) electron lucent vesicles, which measure 3000–4000 A in diameter. Granules of intermediate size with various density are also present in both types of mice. The electron dense core granules are predominant in DI Os/+ mice, whereas, electron lucent vesicles are predominant in the normal VII +/+ mice. Similar uniform size membrane bound electron dense granules have been observed in ACTH cells of PI and pars distalis. From earlier experimental evidences and the present observations, it is concluded that the dense core granules in PI may be synthesizing ACTH or ACTH-like substance. It is also discussed that these dense core granules may further mature and give rise to MSH in the form of electron lucent vesicles. If it is so, PI light glandular cells may have dual functions, of producing MSH and ACTH. One of the functions of ependymal-like cells, may be the transport of PI secretion. Three types of nerve endings are observed throughout the PI, making synaptic contact with the predominant cell type. The innervation is more in DI Os/+ mice than in normal mice. The classification of these nerves is according to Bargmann and co-workers 1) peptidergic neurosecretory fibers, contain mainly membrane bound dense core granules, measuring 1200 to 1800 A, and are the classic neurosecretory granules; 2) adrenergic fibers, measuring 700–900 A; 3) cholinergic fibers, measuring 300–400 A. Adrenergic and cholinergic fibers are more towards the hypophysial cleft. The increased innervation, the synaptic contact, the extremely hypertrophied PI and the greater activity of its light glandular cells in the DI Os/+ mice show the PI is under the influence of the nervous system.

Electron microscopic observations on the development of the median eminence in perinatal rats.

This paper reports details of the development of the external layer of the median eminence with special reference to the appearance of the nerve terminals, containing electron dense core and electron lucent vesicles, in the outermost layer of a palisade structure (2–3 μ thick). Observations were made on perinatal rats of the Sprague-Dawley strain (16, 18, 20 day fetuses and rats 5 hours, one 4, and 8 days after birth). The palisade structure of the outermost layer of the median eminence was first clearly detectable 5 hours after birth. Concomitantly, there was a marked increase in the number of nerve terminals in this layer. The nerve terminals containing electron dense core and electron lucent vesicles were seen in 18 day fetuses in the outermost layer of the median eminence. These nerve terminals increased in number during development, especially from the 20th day of fetal life to the 4th day after birth. The size range of the majority of the electron lucent vesicles did not change during development, but that of the core vesicles increased from 600–800 A from the 18th to 20th day of fetal life. The initiation of neurohemal control of the adenohypophysial function by the hypothalamus is discussed.

The fine structure of neuroglia in the central nervous system of Nereid polychaetes.

The principal supportive elements of the nereid central nervous system are non-neuronal cells that are referred to as supportive glia. Supportive glial cells form a conspicuous cortex in the nerve cord. The inner region of this cortex consists of closely packed processes and cell bodies of fibrous supportive glial cells that are arranged in concentric layers around the perimeter of the neuropile. The fibrous appearance of the glial cells results from dense bundles of cytoplasmic filaments. Many fibrous glial processes penetrate the neuropile and ramify among the neuronal elements. Larger, irregularly shaped cells are the chief supportive glial elements of the peripheral region of the cortex where they line the stromal sheath (neural lamella) and invest the neuronal perikarya with extensive concentric systems of lamellate processes. These glial cells usually possess a relatively undifferentiated cytoplasm with scattered glycogen granules, but occasionally have a well developed Golgi apparatus, endoplasmic reticulum and densely packed particulate glycogen. The supportive glia exhibits numerous desmosomes as well as 5-layered (“tight”) and 7-layered (“gap”) junctions. Interspersed among the supportive glial cells are non-neuronal cells referred to as granulocytes. These cells have abundant large, granular inclusions, electron lucent vesicles, plasmalemmal infoldings and microtubules. The granulocytes may be derived from undifferentiated glial cells or may represent coelomocytes that have invaded the nervous tissue.

Ultrastructural aspects of cat submandibular glands.

AbstractSubmandibular glands of five adult female cats were examined by conventional electron microscopic techniques. All gland acini are mucous secreting and each acinus is capped with mucous secreting demilunar cells. Secretory product of demilunar cells is more electron lucent than that of acinar cells. The demilunes show intercellular tissue spaces and intercellular canaliculi whereas similar specializations are absent between acinar cells. Mitochondria and arrays of granular endoplasmic reticulum are more numerous in demilunar cells than in acinar cells. In acinar and demilunar cells secretory droplets first appear as enlarged Golgi saccules which subsequently become closely related to cisternae of the granular endoplasmic reticulum. Filamentous structures, interpreted as mucin molecules, are present in secretory droplets of acinar cells. Intercalated ducts are short, consisting of several junctional cells between acini and striated ducts. Striated ducts are long and tortuous and contain light cells, dark cells and basal cells. Light cells contain numerous membrane bound granules in their distal ends whereas dark cells show electron lucent vesicles in the same position. Basal cells contain a paucity of organelles and membrane plications but exhibit hemidesmosomes along their basal plasma membranes. Myoepithelial cells are abundant in relation to acinar and demilunar cells. Nerve terminals are present in some instances between acinar cells or between acinar and myoepithelial cells.

The fine structure of the procerebrum of pulmonate molluscs, Helix and Limax

Neuronal perikarya of the procerebrum of Helix and Limax are generally naked and lie side by side. The cell mass contains large numbers of axosomatic and axoaxonic synapses represented by boutons of two types; dense core vesicles (800–1200 Å, in diameter) being characteristic of the first type and clusters of electron lucent vesicles (500–800 Å) of the second. Endings of the two types occur also in the terminal mass of the neuropile while the internal mass contains peculiar axonal enlargements filled with fine twisted tubuli. Axons containing dense core vesicles seem to correspond to varicose monoaminergic fibres detected by a fluorescent histochemical method.

Functional morphology of the pars intermedia of the rat hypophysis as revealed with the electron microscope. 3. Effects of dexamethasone on the pars intermedia of rats under various experimental conditions.

The general structures of the pars intermedia of the rat hypophysis including two kinds of light cells, dark cells, marginal zone, cysts and nervous elements were described, and effect of dexamethasone on the pars intermedia, especially on the light cells of the first type of intact and experimental rats was studied by electron microscopy.Three hours after a single injection of dexamethasone secretory granules of the light cells of the first type were extremely increased in electron density, but after 3 weeks the electron density of the granules was decreased nearly to the normal level.Prolonged daily injection of dexamethasone caused a cumulative effect on the light cells as an increase of dilated endoplasmic reticulum at 7 days and considerable degeneration of whole cells at 10 days.One day after adrenalectomy the light cells which were also treated with dexamethasone 6 hours after the operation contained numerous clear vesicles, while in later adrenalectomized animals which received dexamethasone 24 hours prior to sacrifice the cells successively increased their dark secretory granules from 3 to 7 days and reached the maximal number at from 10 to 14 days after the operation. Four weeks after adrenalectomy the light cells appeared to have a large cell volume and to contain granules of various densities, extensive Golgi apparatus and cisternae of the endoplasmic reticulum filled with dense material.Two and a half minutes after laparotomy, the light cells which were pretreated with dexamethasone 24 hours before the operation contained a mixture of dark and light granules. The dark granules were decreased in number one day after the operation and were replaced by electron lucent vesicles 3 days after the operation.These results apparently indicated that the release of granule content of the light cells of the pars intermedia was inhibited by dexamethasone which had been known to prevent a release of ACTH from the adenohypophysis, and that the pars intermedia responded to stressful stimuli such as adrenalectomy and laparotomy, showing morphological alterations of the density of secretory granules. The morphological changes showed a good parallelism with changes of blood and pituitary ACTH concentrations. From these findings two possibilities may be suggested either the pars intermedia cells might produce an ACTH-like substance, or the intermedia hormone might be a precursor of ACTH in biosynthesis in the pars distalis.